共查询到20条相似文献,搜索用时 218 毫秒
1.
J. Gilmour 《Marine Biology》1999,135(3):451-462
Laboratory and field experiments were used to determine whether high (≃100 mg l−1), low (≃50 mg l−1) and control (≃0 mg l−1) levels of suspended sediment affected fertilisation, larval survival, and larval settlement in the scleractinian coral Acropora digitifera (Dana, 1846). Both high- and low-sediment treatments significantly decreased fertilisation, but post-fertilisation embryonic
development was not inhibited by suspended sediments. Larval survival and larval settlement were significantly reduced in
high- and low-sediment treatments. No difference was found between high- and low-sediment treatments in any of the three post-spawning
processes investigated, suggesting that they are susceptible to sediment concentrations which are not exceptionally high even
under natural conditions (>50 mg l−1). The introduction of an additional stress in the form of high levels of suspended sediments coupled with naturally high
variability in recruitment may have a considerable effect on the successful supply and settlement of coral larvae to a reef.
Given that many coral communities are open reproductive systems, the consequences of disturbance events are not likely to
be restricted to the impact area. Recruitment to a population may be reduced significantly in the presence of high levels
of suspended sediments because of effects on larval survival and settlement. Recruitment of larvae to adjacent populations
may also be affected due to a decreased fertilisation success and potential increases in mortality of larvae passing through
the affected site.
Received: 13 August 1998 / Accepted: 22 July 1999 相似文献
2.
The Belizean reef coral Agaricia tenuifolia Dana forms aggregations in which rows of thin, upright blades line up behind each other. On average, the spacing between
blades increases with depth and hence with decreasing ambient irradiance. We designed and built a small, inexpensive light
meter and used it to quantify the effect of branch spacing on light levels within colonies at varying distances from branch
tips. Concurrently, we measured photosynthetic pigment concentrations and population densities of symbiotic dinoflagellates
(zooxanthellae) extracted from coral branches of colonies with tight (≤3 cm) vs wide (≥6 cm) branch spacing, collected at
15 to 17 m and from colonies with tight branch spacing collected at 1 to 2 m. Light levels decreased significantly with tighter
branch spacing and with distance from the branch tips. Total cellular pigment concentrations (chlorophylls a, c
2
and peridinin) as well as chlorophyll a:c
2
and chlorophyll a: peridinin ratios all increased significantly with distance from the branch tip, indicating very localized differences in
photoacclimation within individual branches. Zooxanthellae from colonies with widely-spaced branches displayed significantly
lower chlorophyll a:c
2
and chlorophyll a:peridinin ratios, and were present at significantly higher population densities than those from colonies with tightly-spaced
branches collected at the same depth (15 m). Tightly-spaced colonies collected from shallow environments (1 to 2 m) displayed
pigment ratios similar to those from widely-spaced colonies from deeper water (15 m), but maintained zooxanthellae populations
at levels similar to those in tightly-branched colonies from deeper water. Thus, variation in colony morphology (branch spacing
and distance from branch tip) can affect symbiont physiology in a manner comparable to an increase of over 15 m of water depth.
These results show that a host's morphology can strongly determine the microhabitat of its symbionts over very small spatial
scales, and that zooxanthellae can in turn display steep gradients in concordance with these altered physical conditions.
Received: 12 June 1997 / Accepted: 24 June 1997 相似文献
3.
The transparent goby Aphia minuta (Risso, 1810) is one of the main target species of the small-scale fishery off the Island of Majorca. Otolith microstructure
and length-frequency analysis were used to study the age and growth of this species during the 1982/1983 and 1992/1993 fishing
seasons. Daily periodicity of increment formation was determined by experiments with marked otoliths in individuals maintained
in captivity. The length range of the catches during the 11 yr period was between 12 and 49 mm, with a main distribution (89%)
between 24 and 40 mm. Otolith age-readings indicate that the population exploited in the commercial fishery consists of seven
age-groups (2 to 8 mo old), with a very high proportion of individuals (95%) between 3 and 6 mo old. Population growth-curves
revealed no differences between males and females. The growth parameters for the whole population are: asymptotic length,
L
∞ = 53.69 mm; growth coefficient, K = 2.23 yr−1; theoretical age at length zero, t
0 = −0.005 yr. Those individuals of A. minuta caught in Majorca during the winter period reached a maximum age of 7 or 8 mo.
Received: 30 December 1996 / Accepted: 16 April 1997 相似文献
4.
A. I. Arkhipkin 《Marine Biology》1997,129(1):103-111
Statolith microstructure was studied in 56 Ancistrocheirus lesueurii (25 to 423 mm of mantle length, ML) caught in the central-east Atlantic. Statolith growth increments were grouped into three
main growth zones, distinguished mainly by increment width. The second transition in the statolith microstructure (from Zone
2 to Zone 3) coincides with the life history shift from epipelagic and upper mesopelagic to a bathyal habitat. Second-order
bands (mean 27.65 growth increments) and sub-bands (mean 13.6 growth increments) within statolith microstructure appeared
to be related to the lunar cycle. Striking sexual dimorphism is reflected in the age and growth rates: males live ca. 1 yr,
while females only start maturing at this age and obviously live >1.5 yr. A. lesueurii is a slow growing squid, attaining 25 to 30 mm ML at the age of 100 d. After ontogenetic migrations into bathypelagic waters
at ML > 30 to 35 mm, growth rates gradually decrease to the minimum known values for squids. Based on back-calculated hatching
dates, A. lesueurii hatches throughout the year with a peak between November and March.
Received: 28 August 1996 / Accepted: 31 January 1997 相似文献
5.
Genetic heterogeneity among adult and recruit red sea urchins, Strongylocentrotus franciscanus 总被引:1,自引:1,他引:0
Allozyme electrophoresis was used to characterize genetic variation within and among natural populations of the red sea urchin
Strongylocentrotus franciscanus. In 1995 to 1996, adult urchins were sampled from twelve geographically separated populations, seven from northern California
and five from southern California (including Santa Rosa Island). Significant population heterogeneity in allelic frequencies
was observed at five of six polymorphic loci. No geographic pattern of differentiation was evident; neighboring populations
were often more genetically differentiated than distant populations. Northern and southern populations were not consistently
distinguishable at any of the six loci. In order to assess within-population genetic variation and patterns of recruitment,
large samples were collected from several northern California populations in 1996 and 1997, and were divided into three size
classes, roughly representing large adults (>60 mm), medium-sized individuals (31 to 60 mm, “subadults”) and individuals <2 yr
of age (≤30 mm test diam, referred to as “recruits”). Comparisons of allelic counts revealed significant spatial and temporal
differentiation among size-stratified population samples. Recruit samples differed significantly from adult samples collected
at the same locale, and showed extensive between-year variation. Genetic differentiation among recruit samples was much higher
in 1997 than in 1996. Between-year differences within populations were always greater for recruits than for adults. Potential
explanations for the differentiation of recruit samples include pre- and post-settlement natural selection and high interfamily
variance in reproductive success or “sweepstakes” recruitment. Unless recruit differentiation can be attributed to an improbable
combination of strong and spatially diverse selection, such differentiation across northern California populations indicates
that the larval pool is not well mixed geographically (even on spatial scales <20 km), despite long planktonic larval duration.
Received: 6 July 1999 / Accepted: 25 January 2000 相似文献
6.
The distribution and abundance of Japanese common squid [Todarodes pacificus (Steenstrup, 1880)] paralarvae off southern Kyushu Island near the Kuroshio were examined in relation to water types in the
region. Surveys were conducted in 1996 and 1997 using paired, 70 cm diameter Bongo nets. Temperature–salinity plots from 0,
50 and 100 m depths were used to assign sampling stations to three water types: inshore, mixing and Kuroshio. In total, 4103
T. pacificus paralarvae were collected at 59 of 72 stations. Catch densities at positive stations ranged between 8 and 4282 ind./50 m2 sea surface area. Catches during both years were highest in mixing waters, followed by inshore and Kuroshio waters. Total
catches were highest just north of the oceanographic front at the inshore edge of the Kuroshio and declined with increasing
distance away from the front. Catches of paralarvae ≤1.0 mm mantle length also peaked near the front. In both years, ≥85%
of all paralarvae and ≥69% of those ≤1.0 mm mantle length occurred less than 25 km from the front. We conclude that most spawning
off southwest Kyushu occurs near the frontal zone, where Kuroshio and inshore waters meet.
Received: 18 November 1998 / Accepted: 11 May 1999 相似文献
7.
V. J. Harriott 《Marine Biology》1998,132(2):319-325
The growth (extension rate, number of radial branches, skeletal mass, branch diameter) of the␣staghorn coral Acropora formosa (Dana, 1846) was examined at four sites on the Beacon Island platform at Houtman Abrolhos, in subtropical Western Australia
(28°S). Sites were at depths of 7 to 11 m, with variable exposure to weather and swell conditions. Two sites on the western
reef slope were partly exposed to the oceanic swell, and two sites in the lagoon were largely protected from wave action.
Linear extension rate between 1994 and 1995 varied significantly between sites, with greater linear extension at the more
protected lagoonal sites. However, accumulation of skeletal mass per branch and number of newly initiated radial branches
did not vary significantly between the sites. Carbonate was deposited in similar amounts, but either as porous, rapidly extending
branches, or as denser branches which extended more slowly. Branch extension rate over 11.5 mo ranged from a mean of 50.3 mm
(range=13 to 93 mm) at a reef slope site to a mean of 76.0 mm (range=31 to 115 mm) at a sheltered lagoonal site. Mean extension
rates were almost twice that previously reported for this species in Houtman Abrolhos (37 to 43 mm yr−1) from a shallower site where environmental conditions were apparently sub-optimal. Growth was within the range reported for
A. formosa from tropical sites, which is consistent with the relatively high calcification and reef-accretion rates recorded for Houtman
Abrolhos in geological and metabolic studies. The role of reduced coral growth-rate in limiting coral reef formation at high
latitudes remains equivocal.
Received: 19 November 1997 / Accepted: 5 May 1998 相似文献
8.
A. L. Moran 《Marine Biology》1997,128(1):107-114
An understanding of spawning and larval development can be fundamental to interpreting the abundance, distribution, and population
structure of marine invertebrate taxa. Tegula funebralis (A. Adams, 1855), the black turban snail, has been the focus of numerous ecological studies on the Pacific coast of North
America. To date, there are only conflicting and anecdotal reports of spawning, and there is no information on larval or juvenile
development for this conspicuous and abundant species. On 19 September 1995, two individuals of T. funebralis were observed free-spawning gametes into seawater in tanks at the Oregon Institute of Marine Biology. Embryos and larvae
were subsequently reared to metamorphosis and beyond. Development was pelagic and similar to development described for other
trochids, and larvae were observed not to feed at any stage. Larvae began to metamorphose at 5.7 to 6.7 d and settled at 260
μm shell length. Juveniles grew ≃ 10 μm in shell length per day and appeared to feed on detritus. Juveniles lacked some adult
diagnostic shell characters, including two columellar nodes and a closed umbilicus. In the field, small (<3 mm) juveniles
occurred in the adult habitat on all sampling dates between October and March. Small juveniles were found only under rocks
and were most abundant under rocks partially buried in coarse sand, suggesting that juveniles may utilize a specific microhabitat
within the adult T. funebralis habitat.
Received: 7 October 1996 / Accepted: 17 October 1996 相似文献
9.
The relative contribution of dissolved nitrogen (ammonium and dissolved free amino acids DFAAs) to the nitrogen budget of
the reef-building coral Pocillopora damicornis was assessed for colonies growing on control and ammonium-enriched reefs at One Tree Island (southern Great Barrier Reef)
during the ENCORE (Enrichment of Nutrient on Coral Reef; 1993 to 1996) project. P. damicornis acquired ammonium at rates of between 5.1 and 91.8 nmol N cm−2 h−1 which were not affected by nutrient treatment except in the case of one morph. In this case, uptake rates decreased from
80.5 to 42.8 nmol cm−2 h−1 (P < 0.05) on exposure to elevated ammonium over 12 mo. The presence or absence of light during measurement did not influence
the uptake of ammonium ions. Nitrogen budgets revealed that the uptake of ammonium from concentrations of 0.11 to 0.13 μM could completely satisfy the demand of growing P. damicornis for new nitrogen. P. damicornis also took up DFAAs at rates ranging from 4.9 to 9.8 nmol N cm−2 h−1. These rates were higher in the dark than in the light (9.0 vs 5.1 nmol m−2 h−1, P < 0.001). Uptake rates were highest for the amino acids serine, arginine and alanine, and lowest for tyrosine. DFAA concentrations
within the ENCORE microatolls that received ammonium were undetectable, whereas they ranged up to 100 nM within the control microatolls. The contribution of DFAAs to the nitrogen budget of P. damicornis constituted only a small fraction of the nitrogen potentially contributed by ammonium under field conditions. Even at the
highest field concentrations measured during this study, DFAAs could contribute only ≃11.3% of the nitrogen demand of P.␣damicornis. This contribution, however, may be an important source of nitrogen when other sources such as ammonium are scarce or during
periods when high concentrations of DFAAs become sporadically available (e.g. cell breakage during fish-grazing).
Received: 22 April 1998 / Accepted: 3 November 1998 相似文献
10.
I. B. Kuffner 《Marine Biology》2001,138(3):467-476
The effects of water flow and ultraviolet radiation (UVR, 280–400 nm) on the reef coral Porites compressa Dana were explored in a manipulative flume experiment. The aim of this study was to determine whether this coral responds
to changes in the UVR environment by adjusting the tissue concentration of UV-absorbing compounds (mycosporine-like amino
acids, MAAs), and to see whether such an acclimation is affected by water flow. Also, calcification rate and chlorophyll-a concentration were measured during the experiment to estimate the potential costs (in the form of slowed growth and/or reduced
photosynthetic capacity) to the coral–alga symbiosis of being exposed to UVR and producing MAAs. Branches of P. compressa from a single male colony were exposed to high or low flow (15 cm s−1 and 3 cm s−1, respectively) and ambient or no UVR in an outdoor, continuous-flow seawater system. Chlorophyll-a and MAA concentrations were determined after zero, 3 and 6 weeks of exposure to the experimental conditions. Increase in
buoyant weight during the two 3-week periods was used to calculate calcification rate. The presence of UVR had a significant
positive effect on total MAA concentration in the P. compressa colonies; however, there were significant interactions present. In colonies exposed to UVR, MAA concentration increased and
then decreased to initial levels in high water flow, and increased steadily in low water flow. In colonies receiving no UVR,
MAA concentration decreased steadily, declining 23% in 6 weeks. The absence of UVR did not result in higher chlorophyll-a concentrations, but the calcification rate was slightly affected by UVR. This study supports the putative photoprotective
role of MAAs in P. compressa, and suggests that the costs of mitigating the effects of ambient UVR are detectable, but they are very small.
Received: 29 February 2000 / Accepted: 20 September 2000 相似文献
11.
The reproductive biology of the jellyfish Catostylus mosaicus (Quoy and Gaimard 1824) (Scyphozoa: Rhizostomeae) was investigated in New South Wales, Australia. Medusae were gonochoristic.
There was a 1:1 ratio of male and female medusae and there was no evidence of sexual dimorphism. Oocytes arose from the gastrodermis
and maintained contact with the gastrodermis, via trophocytes, throughout gametogenesis. Spermatogenesis occurred within follicles
that arose from invagination of the gastrodermis. Detailed sampling of gonads over a period of 3.25 yr in Botany Bay, and
over 2.5 yr in Lake Illawarra, indicated that gametogenesis occurred almost continuously during the year. Oocytes were smaller,
or were absent from the ovaries during 3 of the 4 winters sampled at Botany Bay and during all 3 winter periods sampled at
Lake Illawarra. Comparisons were made with other locations, although these were sampled less frequently. When medusae were
present at a location, similar trends were observed. The size at which medusae matured varied, but during non-winter periods
and at two locations, all medusae exceeding 130 mm diam were considered mature.
Received: 6 January 2000 / Accepted: 3 July 2000 相似文献
12.
A. G. Grottoli 《Marine Biology》1999,135(3):437-449
Stable-isotope and growth records of coral skeletons are often used to reconstruct tropical paleoclimate, yet few surveys
have systematically examined the natural variability in coral skeletal 13C, 18O and maximum linear skeletal extension (MLSE) across depth. Here, interspecific, intraspecific, and geographical variations
in coral skeletal 13C, 18O, and MLSE were examined in the corals Porites compressa, P. lobata, and Montipora verrucosa grown at 1.7, 5.0, and 8.3 m depth from August 1996 to March 1997 at The Point Reef and Patch Reef #41 field sites in Kaneohe
Bay, Hawaii. Coral skeletal 13C values significantly decreased with depth and differed between species, but did not vary between field sites. 18O values were not significantly different across depth within a species, but did differ among species and field sites. High-resolution
analysis of the intra-annual variation in skeletal 13C and 18O in P. compressa at 2.0 m depth confirms that these isotopes reflect changes in solar irradiance and temperature, respectively. Changes in
MLSE across depth were consistent within, but highly variable among, species. Peak MLSE occurred at 1.7, 5.0, and 8.3 m for
P. lobata, P. compressa, and M. verrucosa, respectively. Such interspecific variation in MLSE patterns may be attributable to one or more of the following: increases
in zooplankton in the diet, changes in metabolic processes, or changes in growth form with depth. Overall, these results imply
that natural inter- and intraspecific variability in coral skeletal 13C, 18O, and MLSE should be considered when interpreting and comparing coral-based tropical paleoclimate data from various coral
species, depths, and field sites.
Received: 6 October 1998 / Accepted: 8 July 1999 相似文献
13.
Effects of dissolved ammonium addition and host feeding with Artemia salina on photoacclimation of the hermatypic coral Stylophora pistillata 总被引:6,自引:0,他引:6
E. Titlyanov K. Bil' I. Fomina T. Titlyanova V. Leletkin N. Eden A. Malkin Z. Dubinsky 《Marine Biology》2000,137(3):463-472
Effects of nutrient treatments on photoacclimation of the hermatypic coral Stylophora pistillata (Esper) were studied. Studies on photoacclimation of colonies from different light regimes in the field were evaluated and
used to design laboratory experiments. Coral colonies were collected in the Gulf of Eilat (Israel) from January to March 1993.
Exterior branches of colonies from different depths (1 to 40 m) displayed different trends in production characteristics at
reduced and very low levels of illumination. From 24 ± 3% to 12 ± 2% of incident surface photosynthetic active radiation (PARo), zooxanthella population density and chlorophyll a+c per 106 zooxanthellae increased, a trend seen in the range of light levels optimal for coral growth (90 to 30% PARo). The P
max of CO2 per 106 zooxanthellae decreased, while P
max of CO2 per 103 polyps increased, indicating an increase in zooxanthella population density at low light levels. Proliferous zooxanthella
frequency (PZF, a measure of zooxanthella division) declined significantly at light levels <18 ± 3% PARo. At the lowest levels of illumination (<5% PARo), zooxanthella population density decreased, as did the PZF; chl a+c per 106 zooxanthellae was unchanged. In 28-d experiments, exterior coral branches from the upper surfaces of colonies from 3 m depth
(65 ± 4% PARo) were incubated in aquaria under bright (80 to 90% PARo), reduced (20 to 30% PARo), and extremely low (2 to 4% PARo) light intensities. At each light intensity, the corals were maintained in three feeding treatments: sea water (SW); ammonium
enriched SW (SW + N); SW with Artemia salina nauplii (SW + A). An increase in P
max of CO2 per 103 polyps was found in corals acclimated to reduced light (20 to 30% PARo) in nutrient-enriched SW, while in SW, where the increase in zooxanthella population density was smaller, it did not occur.
Nutrient enrichments (SW + N at 2 to 4% PARo and SW + A at 20 to 30% PARo) increased zooxanthella population density, but had no effect on chl a+c per 106 zooxanthellae. Acclimation for 14 d to reduced (10 to 20% PARo) and extremely low (1 to 3% PARo) light intensities shifted 14C photoassimilation into glycerol and other compounds (probably glycerides), rather than sugars. Both ammonium addition and
feeding with Artemia salina nauplii resulted in an increase in photosynthetic assimilation of 14C into amino acids. We conclude that acclimation to reduced light consists of two processes: an increase in photosynthetic
pigments and in zooxanthella population density. Both processes require nitrogen, the increase in zooxanthella population
density needing more; this adaptation is therefore limited in nitrogen-poor sea water.
Received: 19 June 1998 / Accepted: 13 June 2000 相似文献
14.
The aim of the present study was to use samples, collected by trawling throughout the year along the lower west coast of
Australia, to determine the reproductive biology, size and age compositions, and growth rate of Urolophus lobatus, a member of a speciose elasmobranch family (Urolophidae) for which there was previously only a small amount of such data.
U. lobatus copulates about 3 months prior to the time when females ovulate, which implies that sperm is stored in the oviducal gland
of the female in the intervening period. Gestation lasts for 10 months, which is relatively long for a species that does not
grow to a large size. This feature is reflected in the fact that the mean disc width at parturition (105 mm) is equivalent
to as much as 44% and 52% of the asymptotic disc widths of the females and males of this species, respectively. The trends
exhibited by the marginal increments on vertebral centra demonstrated that each of the translucent zones in these centra is
laid down annually and that their numbers can thus be used to age this species. Maturity was attained by about 70% of females
and 50% of males at the end of the 4th and 3rd years after conception, respectively, or at just over 3 and 2 years after birth,
respectively. Females and males typically first reach maturity at ˜200 and ∼160 mm, respectively, and attained maximal disc
widths of 277 and 237 mm, respectively. Females reached maximum ages of 15 years from conception and 14 years from birth,
with the corresponding values for males being 13 and 12 years, respectively. Since such a large amount of growth occurs during
gestation, von Bertalanffy growth curves were constructed using the date of conception, that is, the fertilisation date, as
age 0, as is usually the case with teleosts, as well as employing the birth date as age 0, as is typically the case with elasmobranchs.
The growth curves drawn through the points for the disc width-at-age of the older female and male fish gave a slightly better
fit when using, as age 0, the parturition date rather than the conception date. However, the asymptotic disc widths derived
for females and males using the conception date, that is, 241.3 and 202.9 mm, were each still only 7.6 mm less than those
derived using the birth date. Moreover, the fit of the line drawn through the points for the disc width-at-age of fish during
gestation was better using the conception date as age 0 than would be achieved by a backwards extrapolation of the growth
curve using the birth date as age 0.
Received: 6 January 2000 / Accepted: 17 June 2000 相似文献
15.
B. Rinkevich 《Marine Biology》2000,136(5):807-812
“Gardening” of denuded coral reef habitats is a novel restoration approach in which sexual and asexual recruits are used.
The present study aimed at the evaluation of the potentiality for restoration use of different types of small fragments subcloned
from the Red Sea coral species Stylophora pistillata. In situ short-term (24 h, 45Ca method) and long-term (1 year, alizarin Red S vital staining) experiments revealed high variation (up to 70%) in growth
rates between up-growing branches of a specific genet, and that tip ratios in dichotomous branches (n = 880) differ significantly between newly formed and older branches, further emphasizing the within-colony genetic background
for spatial configuration. Small, isolated branches (<4 cm) revealed high survivorship (up to 90%, 1 year) and up to 20–30%
(1 year, single- vs. dichotomous-tip branches, respectively) growth, showing that small-sized branches are suitable for restoration
purposes. Results differed significantly between genets. Total length added for dichotomous-tip branches was in general at
least twice that recorded for single tips of a specific genet. Restoration protocols may be applied either by sacrificing
whole large colonies via pruning high numbers of small fragments or, by pruning only a few small branches from each one of
many genets. An in situ “nursery period” of approximately 8 years is predicted for S. pistillata small fragments.
Received: 17 August 1999 / Accepted: 15 February 2000 相似文献
16.
The seasonality of polypide cycling has been investigated for three species of erect bryozoans from Antarctica: Isoseculiflustra rubefacta (Kluge, 1914), Nematoflustra flagellata (Waters, 1904) and Himantozoum antarcticum (Calvet, 1905). Approximately ten colonies of each species were collected monthly by SCUBA divers over a 14 mo period during
1992/1993, and the status of each individual zooid was classified as differentiating/regenerating, active (feeding autozooids),
degenerate (brown body) or sexually reproductive (ovicells present, or zooid containing a larva). Polypide cycling in all
three species was distinctly seasonal. New zooids formed at the growth margin and typically contained actively feeding polypides
for ≃9 mo before these polypides degenerated into brown bodies in the austral winter (June). Very few polypides were active
in the period from June to August, when water-column food levels were at their lowest; after this period new polypides differentiated.
Individual zooids typically underwent a total of five (I. rubefacta and N. flagellata), or at least four (H. antarcticum) complete polypide cycles before becoming senescent. Polypide lifetimes generally became shorter as the age of the zooid
increased. Sexual reproduction was also distinctly seasonal in these species, with bands of ovicells or sexually reproductive
zooids being formed each year in late summer once a given colony had grown to a threshold size (or age). Larvae were then
brooded for ≃10 mo before being released in January/February (N. flagellata) or February/March (H. antarcticum). The seasonal patterns of polypide cycling are related clearly to the variations in food availability, and these species
appear to have the longest zooid lifetime (≃5 yr) and the slowest polypide cycling (once per year with polypide lifetimes
up to 10 mo) reported for any bryozoan so far.
Received: 7 May 1995 / Accepted: 19 November 1997 相似文献
17.
In this paper we have two goals. First, we examine the effects of sample size on the statistical power to detect a given amount
of inbreeding in social insect populations. The statistical power to detect a given level of inbreeding is largely a function
of the number of colonies sampled. We explore two sampling schemes, one in which a single individual per colony is sampled
for different sample sizes and a second sampling scheme in which constant sampling effort is maintained (the product of the
number of colonies and the number of workers per colony is constant). We find that adding additional workers to a sample from
a colony makes it easier to detect inbreeding in samples from given number of colonies; however, adding more colonies rather
than more workers per colony always gives greater power to detect inbreeding. Because even relatively large amounts of sib-mating
generate relatively small inbreeding coefficients, detection of even substantial deviations from random mating will require
very large samples. Second, we look at the amount of inbreeding in a large population of the western harvest ant, Pogonomyrmex occidentalis. We find deviations from Hardy-Weinberg equilibrium equivalent to approximately 27% sib-mating in our population ( f = 0.09). Review of past studies on the population structure of other Pogonomyrmex species suggests that inbreeding may be a regular feature of the mating system of these ants. Although P. occidentalisis a swarm-mating species, there are a number of features of its population biology which suggest that the effective population
size may be small. These include topographical variation that potentially breaks the population into demes, variation in the
reproductive output of colonies, and variation in the size of reproductives produced by colonies.
Received: 6 May 1996 / Accepted after revision: 6 October 1996 相似文献
18.
Effect of temperature on statolith growth of the European squid Loligo vulgaris during early life 总被引:1,自引:0,他引:1
R. Villanueva 《Marine Biology》2000,136(3):449-460
Over the past decade, statolith interpretation has resulted in a major advance in our knowledge of squid population-dynamics,
but the way in which environmental conditions affect the statolith increment-deposition ratio remains virtually unknown. The
object of the present study was to determine the effect of temperature on this process, using tetracycline marks to validate
statolith growth in Loligo vulgaris Lamarck, 1798 under rearing conditions equivalent to severe winter (11 °C) and summer (19 °C) temperature regimes. Tetracycline
marking was performed every 10 d (at 10, 20, 30, 40, 50 and 60 d of age). The newly hatched squid paralarvae were slightly
smaller in summer than those hatched in winter. Survival rates were similar in both cultures, but growth rates (wet mass)
of summer squids were double those in winter. At hatching, statoliths were already longer in the summer squids, and growth
rates were 2% d−1 as opposed to 0.9% d−1 for winter statoliths. For the dorsal dome area of the statolith, where more increment counts were made, statolith growth
was of 3.25 μm d−1 in summer, and daily increment deposition was confirmed in 87% of the statoliths. The slow growth of statoliths at winter
temperatures yielded a mean growth of 1.1 μm d−1– insufficient to discern the increments using light microscopy. Subsequent SEM observation enabled only 21% of the winter
statoliths to be read; these also indicated a deposition rate of one increment d−1. Since the life span of L. vulgaris is ≃1 yr, squids will experience at least one winter during their life cycle, and this might be visible on the statolith.
Received: 28 June 1999 / Accepted: 20 December 1999 相似文献
19.
The distribution of the phyllosoma larvae and free-swimming pueruli of the Japanese spiny lobster Panulirus japonicus (von Siebold, 1824) has been studied off the south coast of Kyusyu Island. From 1992 to 1995, four research cruises were
conducted on board the R.V. “Yoko-maru”. Cruises were mainly carried out over the new moon period between June and August
along transect lines that cross the Kuroshio Current. In total, 89 later stage Form F phyllosoma (body lengths ≥20 mm) and
43 free-swimming pueruli of P. japonicus were caught; 94.4% of the later stage phyllosoma larvae were in the final stage. The phyllosoma were distributed widely in
and south of the Kuroshio Current, where high-salinity (34.8) water exists at depths below about 80 m. Highest densities of
the final phyllosoma larvae were observed in or near the Kuroshio Current, and molting to the puerulus stage also occurred
in the same area. Free-swimming pueruli were mainly sampled in and north of the Current. It is suggested that the pueruli
of P. japonicus swim across the Kuroshio Current to settle in coastal areas.
Received: 9 December 1996 / Accepted: 25 September 1998 相似文献
20.
The azooxanthellate coral Acabaria biserialis Kükenthal, 1908 (Octocorallia: Alcyonacea) is highly abundant on the vertical underwater structures of the oil jetties at
Eilat (Red Sea), but it is rare on the adjacent natural reefs. To understand its success on such artificial substrata we examined
various aspects of its life history and population dynamics. A. biserialis is a gonochoric brooder. The percentage of colonies on the artificial substrata bearing gonads ranged from none (September
1994 and 1995) to 100% (January 1994, 1995 and April 1994). Mature oocytes and sperm sacs reached rather small maximum diameters
of 240 and 160 μm, respectively, probably dictated by the small gastrovascular cavities. A continuous release of planulae
was observed in the laboratory from March to July 1995. Planulation occurred during various lunar phases, and both by day
and night. Recruitment of A. biserialis on PVC plates attached to the jetties coincided with the breeding period inferred from the laboratory findings. Recruits
reached a maximum height of 3 cm within 3 months, thus exhibiting a remarkably rapid growth rate compared with other gorgonians.
This high colony growth rate may compensate for the lack of clonal propagation in the studied A. biserialis population. The complex substrata of the jetties provide the conditions required for successful colonization, which include
upside-down orientation, an adequate light regime and exposure to flow. The findings of our study may provide a useful contribution
to the design of artificial reefs aimed at attracting rapid colonization by A. biserialis colonies.
Received: 30 December 1998 / Accepted: 19 August 1999 相似文献